HAL'CYON, noun hal'shon. [Latin halcyon; Gr. a king-fisher.] The name anciently given to the king-fisher, otherwise called alcedo; a bird that was said to lay her eggs in nests, on rocks near the sea, during the calm weather about the winter solstice. Hence, HAL'CYON, adjective Calm; quiet; peaceful; undisturbed; happy. halcyon days were seven days before and as many after the winter solstice, when the weather was calm. Hence by halcyon days are now understood days of peace and tranquility.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI